Currently, convergence of a fixed network and a mobile network (Fixed Mobile Convergence, FMC) is a trend. After convergence of a fixed network and a mobile network, in a residential unit, a mobile terminal and a fixed-line device (fixed device) may be both connected a fixed-line gateway node by using a residential gateway. Therefore, both a data flow generated by the mobile terminal and a data flow generated by the fixed-line device need to pass through the residential gateway. As shown in FIG. 1, a data flow 1 that is generated as a mobile terminal activates a first access point, a data flow 2 generated as the mobile terminal activates a second access point, a data flow 3 generated as the mobile terminal performs local data access, and a data flow 4 generated by the fixed-line device all pass through a residential gateway 110, and all data flows (the data flow 1, the data flow 2, the data flow 3, and the data flow 4) that pass through the residential gateway are generally referred to as a data flow 5, and therefore, the data flows 1 to 5 are correlated.
To implement differentiated network services, a operator needs to perform policy control and charging on a data flow. The prior art provides a data flow control method, in which different policy and charging rules function (PCRF) entities are selected according to different terminal identifiers and access point identifiers (Access point Name, APN). It may been learned from the foregoing that, at least one of terminal identifiers and access point identifiers of the data flows 1 to 5 is different. For example, the data flow 1 and the data flow 2 have the same terminal identifiers, but have unique access point identifiers. Therefore, policy control is performed separately on the data flow 1 by using a PCRF entity 1, policy control is performed separately on the data flow 2 by using a PCRF entity 2, policy control is performed separately on the data flow 3 by using a PCRF entity 3, policy control is performed separately on the data flow 4 by using a PCRF entity 4, and policy control is performed separately on the data flow 5 by using a PCRF entity 5.
However, in such a manner, the PCRF entities are independent of each other. If a bandwidth originally occupied by the data flow 5 is 10 megabits, in which a bandwidth allocated to the data flow 1 is 6 megabits, when policy control on the data flow 5 by the PCRF entity 5 changes, that is, a bandwidth occupied by the data flow 5 is reduced from 10 megabits to 5 megabits, and the PCRF entity 1 does not know the change and therefore still performs policy control in accordance with 6 megabits, an exception occurs. For example, it cannot be ensured that the data flow 1 continues to obtain a bandwidth of 6 megabits, because the entire residential gateway can obtain only a bandwidth of 5 megabits. In this case, for the data flow 1, a bandwidth guaranteed for the data flow 1 by a network policy entity actually cannot be fulfilled. In addition, the data flow 1 distributes data packets at a rate of a bandwidth of 5 Mbit/s. Other data flows in the same residential gateway (Residential Gateway, RG), for example, the data flow 2, the data flow 3, and the data flow 4 still perform distribution in accordance with the original data flow rates (which are, for example, 2 Mbit/s, 1 Mbit/s, and 1 Mbit/s, respectively), that is, a data flow of 10 Mbit/s contends for a bandwidth of 5 Mbit/s, which definitely causes nearly a data packet loss of 50% of the entire residential gateway. The quality of service of a service provided for a user is quite low, and service experience of the user is also quite poor.